Drilling mud



' Patented-Dec. 14,1943

DRILLING MUD George E. Cannon, Houston, Tex., assignor to Standard Oil Development Company, a corpo ration of Delaware No Drawing. Application May 15, 194 Serial No. 393.660

2 Claims. (01. 2524.5)

This invention relates to a drilling fluid which will effect a minimum of disintegration of heaving shale.

In the rotary drilling of oil and gas wells a mud fluid is pumped down the drill stem to the drill at the working face in the bottom of the bore. The stream of drilling fluid passes across the working face of the drill and escapes upward through the bore. 'In some areas, notably the Gulf Coast of vTexas and Louisiana. a formation known as heaving shale, must be penetrated before reaching the oil or gas containing reservoirs. It'is dimcult. and often impossible, to

penetrate this formation by ordinary rotary drilling methods and mud fluids. This shale has a tendency to moveinto the hole filling up the hole already drilled and often sticking the drilling tools. It is generally believed that the cause of this action si the hydration of the shale adjacent the bore hole by the water contained in ordinary drilling mud. A heaving shale may be defined as one which in contact with the usual in making up the drilling mud is the weight of mud desired. In drilling wells through various formations the desired weight of the drilling mud-may be' from 8 to 18 pounds per gallon. When making up the lighter weight mud. low concentrations of aluminate may be employed with or without suitable addition of weighting materials. But if heavier drilling muds are rewaterbase drilling fluids swells or disintegrates continuouslyso much as to interfere with the drilling operations.

In accordance with the present invention the disintegration of the heaving shale is prevented by the addition to an ordinary drilling mud of readily soluble aluminates. By ordinary drilling mud is meant the usual mud used in rotary drilling which is comprised of usual colloidal weighting materials, such as clay, mixed with water. Other finely divided weighting materials, such as barytes, iron oxide, and the like, may be used to supplement or as as a substitute for the clay in forming the drilling mud.

As preferred materials selected from this class, sodium' aluminate and potassium aluminate, used either separately or in admixture for conditioning drilling muds, have been found to be most satisfactory. The amount of the conditioning agents to be employed in the drillin fluid may be varied within. a substantial range to compensate for different conditions encountered. The most efiective amount to be used will he usually determined by experimentation, that is,

by obtaining a sample oi heaving shale throughquired, greater amounts of weighting materials must be used, and in general greater concentrations of aluminates will be desirable. In general, it has been found most advantageous to use from 5% to 25% by weight of aluminates in drilling fluids but amounts outside of this range have also been found satisfactory. It may be stated generally that the concentration of the aluminates in drilling muds may be varied through a wide range and the advantages of the invention retained throughout the extent of the variation.

On some occasions, it will also be found a distinct advantage to mix with the aluminates other salts'which are readily soluble and which will aid in controlling the amount of hydrolysis of the aluminates in the solution. In general,

Ireadilysoluble salts having the same metal ions as the aluminates employed have been found to give the most satisfactory results when mixed with the drilling mud to supplement the aluminates. As specific examples sodium chlorides or nitrates have been found to be particularly useful when employed in conjunction with sodium aluminate indrilling fluid and likewise potassium chloride and nitrate have been found useful when employed in like manner with potassium aluminate in drilling fluid.

While I have given specific embodiments of the practice of the present invention, it will be understood that they are given by way. of illustration and not by limitation.

Having thus described the present invention, 

